This study is designed to investigate the aspects of peripheral and central auditory pathology that are necessary for the development of tinnitus. Tinnitus is considered to be a serious, often debilitating handicap. Chronic tinnitus is a symptom experienced by 35% of the U.S. population and 10% of people with chronic tinnitus consider the problem to be severe and to significantly interfere with activities of daily life. Although there has been increased interest in studying tinnitus over the last decade, understanding the pathophysiology of chronic tinnitus remains rudimentary. Consequently there are no uniformly effective treatments for this disorder. The current research will use an animal model of a common type of tinnitus to explore factors that may be critical to developing the phantom auditory perception. Tinnitus will be induced in animals by exposure to noise sufficient induce hearing loss. The tinnitus will be detected and characterized in individual subjects using established psychophysical behavioral techniques. The qualitative aspects of tinnitus will be measured and correlated with functional and morphological changes in the cochlea induced by the noise exposure. Cochlear function will be measured with auditory brainstem response testing and distortion product otoacoustic emissions, and the pattern of noise-induced hair cell damage evaluate with electron microscopy. This study will determine if noise-induced tinnitus is associated with a specific pattern of cochlear damage. The model will also be used to investigate the contribution of the dorsal cochlear nucleus (DCN) to the development of tinnitus. The DNA is an auditory structure in the brainstem that has been implicated as a potential tinnitus generation site. The current research will directly test this notion by examining the effect of DNA ablation on the auditory perception of tinnitus. This research intends to answer fundamental questions concerning mechanisms of tinnitus generation. Safe and efficacious therapy for this prevalent and often debilitating problem can only occur with improved understanding of the disorder.